Pharmacological ovarian stimulation is an accepted technique for amplifying the normal process of follicular development and maturation. It has been in use for the past decade, especially in cases of infertility. Pleural effusion associated with ovarian hyperstimulation syndrome (OHSS), a complication of this therapy, may be more prevalent than is commonly accepted. Four young women presented to our department with dyspnoea caused by pleural effusion as a result of ovarian hyperstimulation syndrome (OHSS). The diagnosis of OHSS was based on a history of pharmacological ovarian stimulation, clinical and laboratory evidence of ovarian enlargement and exclusion of other potential causes of pleural effusion in young women, such as infections, malignancy, pulmonary embolism and collagen vascular diseases. The fluid characteristics in all cases were exudative, with low to normal LDH. All of these patients required fluid evacuation for symptomatic relief. Resolution was achieved with supportive measures and rest. Ovarian hyperstimulation syndrome may be common enough to warrant routine consideration in the differential diagnosis of pleural effusion in young women.